Weeds could help to feed the world

Plants that cope better with changes in the environment – giving greater crop yields in the face of global warming – could be developed following a study into the weeds in the cracks in pavements.

Thale cress

Dr Giles Johnson and his team at The University of Manchester have identified a protein that helps plants ‘track’ the environment and increase their capacity to photosynthesise (capturing light energy through the leaves which enables them to grow). This protein is produced according to the expression of a particular gene.

Some plants, including important crops, are less able to track their environment and are thus unable to cope with environmental changes. But if the team is able to help plants to respond to changes in their environment by traditionally breeding or genetically modifying them, crop yields could be increased, especially in vulnerable land.

The study – which used thale cress, a common weed that is in the same family as cabbage and oil seed rape – is published in Plant Physiology today (26th November 2009).

Dr Johnson, of the Faculty of Life Sciences, said: “Over the last 200 years, industrial society has transformed the atmosphere of our planet, increasing CO2 concentration by 50%. Climates are becoming warmer but, crucially, more unstable with increasing frequencies of extreme weather events such as droughts and heat waves – it is this variability of climate that poses most threat to agriculture. Even short periods of extreme weather can trigger crop failure.

“If we wish to secure food production, we urgently need to breed plants with an increased ability to tolerate change in their environment.”

He and his team grew thale cress at low light then transferred it to high light for nine days, which resulted in a 40% increase in photosynthesis. This corresponded with an increase in the expression of a gene that encoded the production of the protein GPT2. This process, in which fully developed leaves change their photosynthetic capacity, is known as dynamic acclimation.

However the team found that if the gene was disrupted, the thale cress was unable to undergo dynamic acclimation and respond well to the changes in environment.

Since crops such as wheat, rice and barley are less able to track the environment, they may be unable to express the gene that triggers production of the protein GPT2. The team believe that ultimately, we could breed this ability into those plants through genetic modification or a selective breeding programme.

Dr Johnson said: “Seed production is 60% lower in plants that are unable to cope with environmental change, which you can translate into a farmer’s yield. Wheat cannot dynamically acclimate, we don’t yet know why, but may be able to induce that ability.

“Some members of the public have their misgivings about genetically modifying crops. However we urgently need to improve our crop yields and must use all the tools available to us.

“Climate change means increasing extreme weather; meanwhile the world’s population is growing and the use of fertilisers is expensive in terms of production and oil costs.

“In addition we need to make the crops give better yields because we haven’t got any more land to spread into. In fact we are losing agricultural land due to irrigation strategies that increase its salt content.

“Finally the recent Royal Society report said we would need to double productivity by 2050 to meet UN goals on poverty.”

The team now plan to study the genetic basis of the process further to find out how the trait of responding to environmental changes can be transferred to other plants.